High temperature resistant vitreous inorganic fiber

Abstract

A low shrinkage, high temperature resistant vitreous inorganic fiber having a use temperature up to at least 1330° C., which maintains mechanical integrity after exposure to the use temperature and which is non-durable in physiological fluids, is prepared by the method of forming a melt with ingredients including greater than 71.25 weight percent silica, 0 to about 20 weight percent magnesia, and about 5 to about 28.55 weight percent of calcia, 0 to about 5 weight percent zirconia, and optionally a viscosity modifier in an amount effective to render the product fiberizable; and producing fibers from the melt.

Description

[0001] This application claims the benefit of the filing date, under 35 U.S.C. .sctn. 119(e), of U.S. Provisional Application for Patent Serial No. 60 / 347,590, filed on Jan. 10, 2002.[0002] The insulation material industry has determined that it is desirable to utilize fibers in heat and sound insulating applications which are not durable in physiological fluids, such as lung fluid. While candidate materials have been proposed, the use temperature limit of these materials have not been high enough to accommodate many of the applications to which high temperature resistant fibers, including vitreous fibers and ceramic fibers, are applied. In particular, high temperature resistant fibers should exhibit minimal linear shrinkage at expected exposure temperatures, in order to provide effective thermal protection to the article being insulated.[0003] Many compositions within the man-made vitreous fiber family of materials have been proposed which are decomposable in a physiological medium...

AI Technical Summary

Benefits of technology

[0029] High temperature resistant inorganic vitreous fibers are provided which are non-durable in physiological fluids. The fibers exhibit a temperature use limit of up to 1330.degree. C., or greater. At these high temperatures, fibers of the present invention as described below undergo less than about 20% linear shrinkage when held at the temperature for 24 hours. Shrinkage resistance is excellent at service temperatures up to 1260.degree. C. with the fibers exhibiting less than about 5% shrinkage when held at 1260.degree. C. for 24 hours. The fibers of the present invention are non-brittle and retain mechanical strength as shown by testing after exposure to service temperatures of 1260.degree. C.

[0034] The present invention provides a process for the production of low shrinkage, high temperature resistant inorganic fiber having a use temperature up to at least 1330.degree. C., which maintains mechanical integrity after exposure to the use temperature and which is non-durable in physiological fluids, including forming a melt with ingredients comprising greater than 71.25 weight percent silica, 0 to about 20 weight percent magnesia, about 5 to about 28.75 weight percent calcia, 0 to about 5 weight percent zirconia, and optionally a viscosity modifier in an amount effective to render the product fiberizable; optionally up to about 3.5% alumina, preferably up to about 2.5 weight percent alumina, more preferably up to about 1.5 weight percent alumina, and up to about 1.5 wt / % Fe.sub.2O.sub.3; and producing fibers from the melt. In a further embodiment, the fiber preferably contains up to about 1.5 weight percent alumina and not more than about 1.5 weight percent iron oxides (calculated as Fe.sub.2O.sub.3).

[0038] The melt compositions utilized to produce the fibers of the present invention provide a melt viscosity suitable for blowing or spinning fiber, and for imparting mechanical strength to the resultant fibers after exposure to service temperature.

[0057] By this testing criteria, a poorly performing pad would have low values for compressive strength indicating that it is easily compressed, and low values for compression recovery indicating that once deformed the pad experiences little recovery. Conversely, a pad / fiber composition with high values for these parameters exhibits high mechanical strength and is considered a good-performer. An ideal fiber would have a compressive strength within a target range comparable to a standard, commercial aluminosilicate fiber, and additionally having high compression recovery, or resiliency.

[0062] According to one embodiment of the present invention, the inorganic fiber is capable of withstanding a use temperature of at least up to 1330.degree. C. with less than about 20% linear shrinkage, exhibits low after service friability, and is non-durable in physiological fluids, such as lung fluid. The non-durable refractory inorganic fiber of the present invention comprises the fiberization product of greater than 71.25 weight percent silica, 0 to about 20 weight percent magnesia, about 5 to about 28.5 weight percent calcia, and optionally a viscosity modifier in an amount effective to render the product fiberizable. The fiber preferably contains up to about 3.5 weight percent alumina, more preferably up to about 2.5 weight percent alumina, most preferably up to about 1.75 weight percent alumina; and not more than about 1.5 weight percent iron oxides (calculated as Fe.sub.2O.sub.3), more preferably not more than about 1.15 weight percent iron oxides. The viscosity modifier may be selected from alumina, boria, and mixtures thereof. Other elements or compounds may be utilized as viscosity modifiers which, when added to the melt, affect the melt viscosity so as to approximate the profile, or shape, of the viscosity / temperature curve of a melt that is readily fiberizable, without having a detrimental affect on the fiber properties.

Problems solved by technology

While candidate materials have been proposed, the use temperature limit of these materials have not been high enough to accommodate many of the applications to which high temperature resistant fibers, including vitreous fibers and ceramic fibers, are applied.

These fibers generally have a significant alkali metal oxide content, which often results in a low use temperature limit.

), phosphorus oxide at levels as low as a few percent can cause severe degradation and / or erosion of furnace components.

The fibers described in the above identified patent publications are limited, however, in their use temperature, and are therefore unsuitable for high temperature insulation applications, such as furnace linings for use above 1000.degree. C., and reinforcement applications such as metal matrix composites and friction applications.

The poorly fiberized fibers manufactured according to the teachings of WO 93 / 15028 or WO 94 / 15883, do not possess adequate shrinkage and / or solubility properties and, therefore, would not be suitable for use as high temperature resistant insulation.

The more friable a fiber, that is, the more easily it is crushed or crumbled to a powder, the less mechanical integrity it possesses.

This results in the fiber's lacking the strength or mechanical integrity after exposure to the service temperature, to be able to provide the necessary structure to accomplish its insulating purpose.

Images